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Nov. 1, 1927; 1,647,468

F. E- PERNOT ELECTRIC TELEGRAPH APPARATUS Filed Oct. 27, 1923 4 Sheets-Sheet 1 u. b z

In re 7110 r Nov. 1, 1927.

F. E. PERNOT ELECTRIC TELEGRAPH APPARATUS Filed Oct. 27, 1923 4 Sheets-Sheet 2 Nov. 1, 1927. 1,647,468 r F. E. PERNOT ELECTRIC TELEGRAPH APPARATUS Filed 00* 2 1923 4 Sheets-Sheet 3 L I I Nov. 1, 1927.

F. E. PERNOT TELEGRAPH APPARATUS ELECTRIC Filed Oct. 27, 1923 4 Sheets-Sheet 4 Patented Nov. 1, 1927.

UNITED STATES PATENT OFFICE.

FREDERICK EUGENE I'ERNOT, OF WASHINGTON. DISTRICT OF COLUMBIA.

ELECTRIC TELEGRAPH APIARATUS.

Application filed October 27, 1923, Serial No. 671,138, and in Great Britain October 28, 1922.

The present invention has reference to methods and means for maintaining synchronous operation of apparatus located at different positions in a telegraph system or in general between electric impulses and a mechanical motion, and has particular although not exclusive application to submarinetelegraph systems.

,The principal object of the present invention is to insure that any or allof the apparatusconcerned. in the handling of telegraph messages at the two .endszof a system for transmission are driven at equal speeds and are maintained in substantially constant relative phase positions Speed, in the sense used here does not necessarily mean rotational speed, 'butmay include frequency of reciprocation for reciprocating parts, or in general, the frequency .of recurrence of recurrent. operations.

Thefprmcipal feature of the present invention isthe utilization of current impulses such as are constituted by signals to compel and preserve the synchronous operation of apparatus; I

Another feature of theinvention consists in providing a mechanism i which. synchronizes with phenomena recurrent at integral multiplesor aliquot parts :of the period o the elemental impulses.

.Ajurther. feature of the invention consists/inutilizing current changes incidental to the signals for efi'ecting speed control.

A subsidiary feature of the invention is the utilization of the end or ends of signals in the process of speed control.

Still another feature of the invention consists in the provision of means for producing electric impulses corresponding to the beginning and/or ending of each signal. v

A further feature consequent upon the last preceding feature consists in suppressing impulses in one direction so that only impulses corresponding to one end of, each signal are retained.

A still further feature of the invention comprises the Provision of means; whercl r the speed corrective eiiort of the impulses is applied in such a direction as to reduce any accumulated phase deviation.

Yet another feature or" the invention is found in the provision or" means whereby through the medium of the speed controlled apparatus the received signals are re-translated for ire-transmission or other purposes.

A still further feature of the invention consists in the transmission of current variatrons when signals are not being sent over the line for the purpose of maintaining the speed control.

A further feature of the invention is to be found in the means whereby either Morse or cable code signals are made eifectivein exerting the desired control.

Further features of the invention will be more fully appreciated from the-following descr ption and appended claims gand" in order that the invention and itsfmode of operation may be completely understood. reference will now be made to the ac'com panying diagrammatic drawin -wherein.: Fig 1 represents one embo iment of-= the invention.

Fig. 2 represents the electrical conditions as functions of time in differentportions of the system for single or double current Morse signals.

Fig.3 is adapted toillustrate the connect tion of a system acording to this in a cable transmission system.

Fig. 4. represents the electrical conditions as I'unctions'of time in difi'erentportions of a cable transmission system in accordance with this invention utilizing double current Morsesignals. Fig. 5 illustrates a method of securing impulses corresponding only to. one end of each signal. Fig. 6 is a modification and i o Fig. 7 is adapted to illustrate a complete system in accordance with this invention.

One embodiment (if the. present invention is shown in Figure 1 wherein an. electric motor M is made. to run in synchronism with the unit signal impulses of theMorse, code, and wherein the method is asffollow sii At A in Figure 1 are the terminals at which powerful subztantially square topped Morse electric currentsignals are available (as at receiving station). In addition to apparatus concerned with the reception and utilization of the signals (not shown in the figure), there is connected to the terminals A the primary vinding T of a transformer'or coupled circuit. A condenser C and resist mice R, associated with t e primary invention winding of the transformer for reasons to be given later. The secondary windin; T of the transformer (or coupled circuit) with its associated condenser is connected to the filament F and grid n of a thrce-elcc trode thermionic valve. steady source e is put in the grid circuit to maintain the grid potential normally at such a. alue that the plate or anode current is in :t at the point of becoming appreciahle. The plate circuit of the valve contains a battery B and goes from the anode P and filament F by way of leads g and g to a continuously operated reversing switch or equivalent device S. The reversing switch S may he of any one of several well known types, and is operated synchronously with and by the motor M whose speed is to be controlled. The circuit leaving the reversing switch passes byleads h and k through resistance R to an auxiliary field winding F of the motor -M. fA condenser C is connected in shunt with the auxiliary field winding F The motor M is shown in this care as a shunt motor with normal field winding F and power supply E.

' To describe the manner of working of the system shown in Figure 1 reference is made to- Figure 2 wherein are depicted the electical conditions as functions of time in different portions of the system. Curve a, shows square topped Morse signals representing the letter F. The zero line is not shown-because the operation of the system shownin Figure 1 is independent of the datum of current about which the signals 7 are formed, so that (I, may represent either single or double current -Morse signals. The signals are characterized by sudden changes indicated at 1, 2 3, 4, etc. in Figure. 2, curve a"'o'f M[ F.' atthe terminalsA'of Figure 1. These sudden changes actupon the primary T; of tlie transformers-lid produce current variations therein which in turn cause in,the secondary T transient volt-age impulsesf -Th es' transient Voltage impulses shown as'cu r ve b, in Figure 2 are impressed upon the valve grid G in Figure 1. The shapes of the transient currents and voltage impulses are controlled by the resistance R, and con densers C; and 2 in a manner well known in th e'theory of coupled elect'ricvcir'ceits, and it. is desirable so to adjust these circuit elements as'to produce in the cu rve 5L substantia llysymmetrical voltage impulses.

" .oqr' e in Figure 2 shows the current resulting in the anode or plate circuit and 9 of the valve. T he positive impulses 1' 3 ie tc on the grid resulting from the sudden ri S e s1, 3 etcfin the s gnal F). M. F. reproduce themselves in the plate current at 1", 3", etc, but the negative ungulses :2 4.

j6, etc., resulting from the suddendrops *2 4, 6 etc. in the signal E. M. F. do not appear in anyway in the plate circuit of the valve, he-

cause of the well known uni-lateral characteristics of the valve. Thus, there are produced in the plate output circuit and f unidirectional impulses corresponding to the sudden rises only in the signal E. M. F. It is the function of the transformer and valve to produce these impulses, and it is the function of theremainder of the apparatus shown in Figure 1 so to utili ze these impulses as to compel the motor M to run synchronously with phenomena recurrent at integral multiples of the period of the elemental signal: that is, the motor M synchronizes with the signal fronts l', 3, 5, etc."oIf dots and dashes because from the nature of the code the time interval between any consecutiye current rises is an int egral niultiple'of 'the time interval between" consecutive current rises when only dots are being sent.

The plate circuit current c,"i n Figure 2 is taken to the auxiliary field winding'F in Figure 1 through a reversing switeh'S'whieh is operated continuously by the 'r'notbr'M'a't approxin'iately (exactly so after the'syn'chronizing action of the invention" b e' il'ig '"de' scribed is brought into play)'tlie'frduency of the signal dots; that is; t-worev eis'all's take place within the time duration of adot. The current supply toithe a'uXili a'r'y't ield' winding F depends in direction'n'pon' t-hepositionbe cupied by newness? iLet 'us iiovvkuppose that conditions for the n'iOthrMai-e such that it is running xqcnyi rsyn nm nism with arriving' dtits, and tha't' the" phase of switch operation is such that 'lhe'reversals take place e vactly'alt the center of th plate circuit current impulses c,' then 'the imp n'lse impressed upon the auxiliary ield winding F; will be as shown in ci l rve d; Figure 2, and consists of equ'al'positiveQa'ndjYegative half impulses. The resultant iivtira"efield excitation 'is unchanged and'themot'ofitlirefore continues to .run at t'hfesarne' spee d ind i the same-phase (measured hy 'thereIati n of switch reversal td'agriviiigslgharmint) as though th'eainiiliary' t iId"F ;'were :not present i Now suppose that from some cause the load on the motor iSliQhtenc QS'o'Qthat its speed increases slightly. The phase of switch operation will tlien be advanced with reference to the irnpulses g iirftlie platejcirciiit, ant instead of equal and 6pp6site"ha1f impulses a-s sho wn" in' 'csi've Z'lfh'eing limpressed upon 'theauxiliary fieldF 'fithe'iie will be impressed impi ilesof the'typ e shown by curve e, of FigiireQ. Thesejinp'iils'sare of a one. red character, andfbcauis of't-he preponderance of current in one direction the resultant field of the motor is altere'd a'ndits speed thereby afle'cted. By a pr'ope'rchoice of the direction of connecting to the field. wind- F this alteration in average field excitation can be made to cause the motor to run more slowly, thereby nentrali g in g the origi-' zfllllctionl'df the speed of signalling.

output terminals of the polarized relay naltendency towards higher speed. Having established the proper direction of connection.'then slow running of the motor will cause aslight lag in phase of switch operation and this in turn results in an alteration of the average excitation in such a direction as to cause the motor to run faster and thus restore the original proper speed.

It will be noticed that the synchronizing systems herein described possess in common with all other synchronizing systems this feature, namely, that a slight alteration in phase is required to bring into operation those forces which prevent an indefinite increase in phase deviation.

It will be obvious that the above method as so far described in its application to Morse code signalling, can equally well be employed in connection with the well known Baudot system of signalling. or with any other system of signalling in which the E. M. F. and current changes occur at, times which-, in principle, are precise and definite. and which'are separated by definite integral multiples of a time element which is a simph: This general adaptability is partially illustrated in-.'Figures 3 and 4. In Figure 3 is shown a'cable system comprising a cable 0, earth 4, double-current Morse transmitting apparatusXat the-end 1 of the cable and a r ceivi ngflrelay 3 at the end 2 of the cable. From the receiving relay 3 go leads 5 to apparati'is concerned with the reception and utilization of the signals, and also from the receiving. relaygoleads 6, connected either inseries with or, as shown, in parallel with the leads 5, to connect to and operate a polarized relay 7; All of the devices indicated in the.=figure;areiwell known in the art. The are at- A andi to -these terminals and including a battery,:the apparatus as shown in Figure 1 are to beiconnected.

InFi me t the curve a: shows the doublecurrent orse signals'delivered to the end 1 of-the-ic'able O in Figure 3. The curve 1-.

in Figure i shows the signals substantially as received and as delivered by the receiving relay 3. at the end 2 of the cable. Because of the greatattenuation along the cable the dots do not appear individually in the curve 1', but only make themselves apparent.- by a zeroaverage current. It, now, the polarized relay 7 .in Figure 3 be adjusted in a. well known manner to have a marking bias, then its contact tongue will remain on the spacing side only so long as a. negative or spacing current flows through the relay winding. When the relay current becomes zero or positive as for a marking current. then the relay tongue will move over to the marking side under the action of the bias, ted it" ll S0 happens by the marking current in the winding, and the result, therefore, of the signals as shown by curve 1". applied to the relay winding is to produce an output from the relay as shown by the curve a. in Figure 4. The changes 1. 3, and-5 from negative to positive in curve a. representing the output from the relay occur substantially coiiicidently with the changes 1, 3.and5 rom spacing current in the signal curve r, of Figure 4. Furthermore, the changes 1,

3. and 5 of curve (1. occur at instants cone-'7 spending to the beginnings of signal elements in curve a). It will be observed that. the positive current in curve a, lasts throughout the duration of a letter, so that, in fact,

the arrangement just described in connection with Figure 3 works only upon the beginnings and endings of letter spaces. or spaces. or similar periods of considerable duration wherein spacing current is sent to line at the transmitting end of the cable, for it is only during such spacing current intervals that a negative or spacing current affects the relay 7 in Figure 3. If, now the terminals A in Figure 3 are made to con- 7 sequent upon the signals represented. by 1" curve a. of Figure 4 impressed upon the primary winding.

It is obvious that the point of and manner of action in the production of transient impulses can be altered by changing'the bias I or polarization of the relay 7 in Figure"3, and any of the several possible modifications based upon such changes can be utilized equally well in etl'ecting the purposes of the present invention. i

In cases such as that described in regard to Morse code signals, it. is characteristic of such signals that all changes of current incident to the beginnings (or endings) of siguzil elements are in the same direction and spaced in time by integral multiples-of a fundamental time period. -In the case of cable code signals the two conditions above are not. fulfilled. The beginnings (or endings) of all signal eleTnent-s are spaced in time by integral multiples of a fundamental time period. but these. changes may be in either direction. As a consequence, therefore. the system as described in connection with Figure l is not. applicable directly when supplied with cable code signals. It can readily be made operable, however, by inserting ahead of it a non-polarized or equivalent relay which acts to change the cable code signals into signals all in the same direction. A centre-zero polarized relay with ,the two contacts joined togetherserves to do this as well as anon-polarized relay.

'The system shown inFigure 1 comprises several distinct parts each of which performs acharacteristic type of function. all, however, working towards-the control of the speed of the motor M.

1. The transformer or coupled circuit T and T produces electric impulses corre sponding to the beginnings and endings of signalsgrthat is, at thoseplaces within the signals most definitely-located in relation to time, where their time-derivative is a. maxivmum.

2. The-thermo-ionicvalve whose function is .to shut out those impulses in a negative direction and thus. retain only impulses cor- .respondingto-one end of a single impulse.

3. A reversing.switclnrigidly o erated by the motor or other mechanism wiosespeed iscto be controlled .and whose functionis to .apply the-,speed-corrective efiort of the impulses insuch a direction as to reduce any accumulated phase deviation.

' lt is -obvionsithat the three several functions above may be performed in diverse ways many .;kinds ofmech anisms, all of which result; in the same thing,- namely, the maintenance of substantial synchronisni betr s 19m aupare e e iin m ns si na s- The third function above,is best performed ina n1annerdescribed -by myself and another British patent specification 196971, whereby correctiveeffort consequent upon a deviatignofphase is madefirst to correct the phase deviation by removal and then e lyi r een-ex enhd pende up th i te va qt a Phas o ec io wa t the re s aster eq i e les equ n -thes .c rr t q r r i I k s-rd t th r nc i a o an I impulse .of current .corr.esponding. to the besa ens ta endin ais g cen'ibe cure in several Ways astfor instance, ;as shown Eigure by means of a condenser andrelay-opereted bythe signals. In Figure 5;at A are shown terminals at which signals are available; for example assume signals pf t he type given by curve 1", in Figure 4. The windingfi of a olarized relay is connected to these terminals, vand the tongue ,9 of the relay, plays between the two contacts 10 and 11 to which is connected a battery12. The relayis adjusted to have marking,bias so that the tongue 9 makes contact with themark -contact 10 unless a negative or spacingpurrent flows in the winding 8. Lead 14 from; the tongue Scontains a series condenser 15, and another lead 13 is taken .from the mid point of the battery 12. At the terminals B of leads 14 and-13 there will appear transient impulses exactly like the impulses shown in curve I), of Figure 4 when the received signals at terminals A are like scribed in connection with Figure 5.

to result inthe suppression of dots those of curve r in Figure 4;. These impulses at, terminals B ,are also of the same typeas those shown by curve ,6, ot'Figure '2, and

hence may be utilized in theilmanner .de-

scribed in connection with Figural wherein a thermo-ionic valve is used to produce a uni-lateral etlect or, alternatively the unilateral etl'ect may-be secured through the use of a polarized relay as further to be (if; Figure 5 the terminals B of leads Hand 13 are connected to the winding 16 of a polarized relay whose function is to replace the valve of Figure 1. The relay tongue 17 is adjusted with a slight spacing bias to cause it to rest normally upon blank contact '19. A positive current in the windinglti causes the tongue 17 to make contact with contact 18 and thus by means. .of lead QOand '21 and hattery 22 energizes the circuit as shown terminating at terminals C. The impulses delivered to terminals C are-thus all in one direction and consequent upon only. the positive impulses present at =terminals B. 'Hence the impulses at terminals C are-identical with those shown by curve oin Figure 2-.and can be used subsequently .as dscribed in connection with Figure 1 0r inanycalternative methods. The-net result of-the arrangement shown in ;Figure 5.:isl to. deliver-at: terminuls C one-way iimpulses "corresponding .to the termiuationsof the letter spaces inireceived signals ofithe .kind shown by curve .'r in Figure 4,1which are thosenormallyconslerment upon double current Morse working over a submarine cable at a speed suflicient as mentioned. i

As indicated in Figure Lthe speed corrective efi'ortis derived'through'the:action of the impulses 1 directly up'on Hahe motor through the auxiliary field winding-as de- .scribed.

These corrective eflorts are only momentary but a continuity ofxapplication can be-secured :by causing the corrective impulse to actuate rfirst vajtlazysto ng relay and then to secure the speed corrective-eflort through the contacts controlled-by this relay. Such a method permits of the control of much stronger forces' or greater power than can be secured from the 'impulsesthemselves. V i i Figurefi shows an alternative-method of producing one-way impulsesin a circuit to correspond to either'thebeginnings or ends of signals. At A arei-terminals from which are delivered signals "or, idor e'xample, the type shown in curve 1', of Figure 4,-and-to these terminals is connected the-windingg 23 of a polarized relay. The relay is given-a marking bias so that the tongue '24 makes contact at 26 except when a spacing current flows in its winding23fin which-caseitis held against the idle back contact 25. Therefore, in the .receptionof signals like those indicated by curve 1 in Figure 4 the tongue makes contact with 26 during the whole of every letter or equivalent. Lead 28 containing a battery 27 makes connection with contact 26 and passes through a relay tongue 30 and back to contact 32 thereof and thence by wayof lead 33 to one of the terminals C. The other terminal C is joined by leads 34 and 29 to thepolarized relay tongue 24. When relay tongue 24 closes on contact 26 an electric impulse is delivered to terminals C through the circuit just described, including the auxiliary relay contact 30 to 32. The relay tongue 30 is controlled by a magnet 31 around which is connected a condenser 36. The magnet 31 and its condenser shunt 36 are connected through resist ance 35 to leads 28 and 29. Upon closing of the contacts 24 and 26 the magnet 31 is energized, but because of the resistance 35 and condenser 36 it becomes magnetized slowly in accordance with wellknown principles so that a definite and determinable (depending on condenser 36 and resistance 35 as well as upon the self inductance of the winding 31) length of time elapses between the closing of contacts 24 and 26 and the opening of the contacts 30-and 32. Thus it is only during this period oftime that the terminals C are energized consequent upon the closing of contacts 24 and 26. When these contacts open consequent upon the re-establishment of spacing current in the relay winding 23 no impulse appears at terminals C. The device shown, therefore, performs both functionsl. and 2 listed above, and delivers at terminals C impulses of the type shown at c iii-Figure 2, that is, in one direction only and-.at cnly the-beginning of a signal. Following after the terminals C may be connected the reversing switch, etc., of Figure 1 for'fthe purpose :of. utilizing the impulses in themaintenance of. synchronism as described. The method just described in connection 'with. .-Figure 6 offers a considerable advantage in the fact that the impulses are obtained directly from the closing of contacts in a battery circuit and do not depend upon the discharge of energy from an "energy-storing field such as a condenser, or

upon transients produced by inductively coupled circuits. The advantage is a practical one concerned in the behaviour of contacts under the action of interrupted currents;

Agreat advantage attaching to the use of synchronous apparatus at the ends of a telegraph cable system is that the dots, which be cause of great attenuation along the cable do not appear individually, can be produced locally at the receiving end at exactly the proper rate and in the proper position relative to the dashes. In general, the use of synchronism makes possible the reformation of incoming signals and the retransmission those previously described for the reception reformation, and the re-transmission ofsig nals from one cable into another. The apparatus is shown (for the sake of simplicity), as connected to a non-duplexed cable, but the method of application to a pair of duplexed cables by'the use of two of such systemsis obvious.

In Figure 7 a cable 37 has transmitted to it by transmitter 39 connected to earth 38 At the receiving-end 41 cable code signals.

so i

of the cable the signals afterv passing".

through the inductances and condensersordinarily used to help in shaping (but not shown in the figure) are taken to the receiving relay coil 42 and thence to with 40'; As 9 is common in practice, the antenna 43of the" coil 42 plays between the butts 44 and 45 making a contact with 44 (for example) for dots P e current, and with'45' f -"100.

dashes or negative current. The two 'halves 46 and 47 of a battery are connected between the butts 44 and 45. The antenna 43 is connected by lead 49 to the winding 51 'ofa centre-Zero relay (whose 'use willfbe' de-' scribed later) and thence byway 'of lead' to the winding 52 of another centre' zerorelay and thence by way of lead 48 to"t he middle of the battery 46 and 47.

The relay winding 52 constitutes the be ginning of the synchronizing apparatus. It carries currents delivered'by the antenna 43 through its butt contacts; that is, the signal current which ordinarily constitutes block signals. The tongue 53 of the relay whose winding is 52 plays between the contacts 54 and 55 but since contacts 54 and 55 are joined together as shown the current produced by battery 57 in the circuit through tongue 53 and either contact 54 or 55 is always in the same direction through the apparatus 57 fed by the circuit just named. The relay 52 and 53 therefore, performs the necessary operation of rectifying the reversed current impulses of cable code signals.

The apparatus 57 supplied with rectified signals as described above consists of the system shown in Figure 6 or equivalent thereto, and whose function is to produce momenlazy oncaray impulses at the beginnings of. signal elements as described in connection lift) with Figure 6. The output leads 58 and 59 from apparatus 57 (corresponding to leads from'terminals C in Figure 6) go to a commutating or, as shown in Figure 7, a reversingf device consisting of two half segments of a slip rin (30 upon which bear brushes 61 and 62. The slip ring 60 is mounted on or driven by the shaft (5% whose speed is to be controlled. It is the function of the Slip ringand brush-2s to control the direction of: the current impulse from apparatus 57 so as to cause it to actuate further apparatus in the proper direction to correct any error in phase position of the rotating shaft 64 with reference to incoming signals. It is degii able to arrange the brushes 61 and 62 in a suitable manner to permit rotation by hand aboutthe axis so that the datum point about which phase correction tal-zes place can be selected at will.

The shaft 64 is driven through ditierentiai gearing comprising master gears 65 and (ST withtwo idler pinions (S8 and 68 mounted within a ring (or equivalently) 69, the outer periphery of which is cut to form a gear. (hen the idler ring is held stationary than the shaft (Si is driven by gear 65 at the same speed'as gear 67' which, in turn, is driven by the motor 66 through shaft 6 k. of shaft 64'can be advanced or retarded by rotatiu'glth'e idler ring 69, and this advance or retardation of phase is what is controlled by the electric impulses delivered through brushes (Stand 62 to the winding 63 of a centre-zero polarized relay. The direction of impulse current in the winding 63 depends upon the position beneath the brushesGl and 62 of the segmental slip ring 60. Forone, say positive, direction of current the relay tongue'SO is deflected upwards against contact 79; Current then flows from battery 82 tlrr'ougli' contact 80 and 79, magnet winding 7S ,"and lead 83. This energizes magnet 78 and draws down the armature against the force of the restraining spring 76. Pawl '1 guided by studs 77 engages the ratchet wheel 72 and turns it a little. This acts through shaft il and gear 70 upon the idler ring 69, thus slightly a tering the phase of shaft 6st and whatever members are attached thereto or operated thereby. By a proper choice of direction of connection and position of brushes 6i and ("r2 this movement can be'm'ade to constitute a cor ection to an error in phase position. No correction takes place when the impulse delivered from the ap aratus 5? consequent upon the beginning of a signal occurs at that instant \rhen'lnuslws (Kl and 62 rest upon the insulation between the'segments of the slip ring (30. Magnet 78, it's armature 7:3, pa l 74 guide studs T7. and restraining spring 76 c nnected by leads 7!) and S3 to the battery S2 and rcla tongue act upon ratche: wheel TI-1 also attached to shaft 71 in a manner identical with that of The phase the corresponding elements 78, 75, 74;(7 and 76 just described to rotate the shaft 71 and gear 70 in the opposite direction consequent upon a negative current through relay winding 63, in which case the tongue 80 makescontact at 79'. A reverse correction is thus obtained for a reversal of impulse current' in brushes 61 and 62.

if the motor 66' runs almost exactly ataspeed corresponding to the frequency of ar-' well known intheart under various-names;

chief of which vis phonic'wheel.- The'current impulses for drivingit areconveniently obtained through contactsoperated by avic-rating reed or tuning iork maintained in" continuous vibration by auxiliary? contacts and a -magnetsimilarto ordinary-.- electric alarums or buzzers.-- A need of this type'is" shown at 91 rigidly supported at: 97. 'A weight 92 onthe reed serves to: adjust'roughl v its frequency. Contact 93; ma net94;and"-' battery 95 serve to maintain the 'reed' in' vibration. Current'from battery 102--fiows'- lhroughlead' 96 and thereed,: and thence alternately through contacts" 98": and 99 th rough leads 100 and 101 *to' the twosv vind ings 104 and-105--of-the motor. Common return to the-battery is'by Mad-103. The motor and reed now run'in synchronism iand' as a result-ofthe redwliaracteristieethe" speed is-maintainedv'ery steady. A spring 90 isattached' to theend ofthe reed 9t antl is constrained'at some point along-its length by the two pins89-mounted'in' a'slidirlg" blOi'k 87. This block move's'al'ong aslide' formedby members 88'under' 'the'acti'on-"of a lead screw '86 which in turn is actuatedby shaft-71 through gears -84 and" 85;" When pins 89 are near to the reed"='91' then the stiffness of'the spring'9O is increased'and'the' frequency-of reedvibrati'ou -is increased, and vice versa. With the gears 84 and'85 and the lead screw 86 as described,- the frequency of reed vibration is tlius gradually -atl'ected y theaccumulation of phase corrections brought about through shaft 71 and ratchets T2 and 73. and by a suitable choiceo'f directlon of thread onlead screw 86'or of the gear connections the changein =vibration frequency of the reed (and hence of motor speed) can be made such as to require less frequent phase corrections.

The shaft 64,- as the result of the-processesdescribed above is driven substantially in synchronism with arriving signals and can be utilized, therefore, to drive mechanisms adapted to retransmit perfectly formed signals corresponding to the more or less distorted block signals as received. The received block signals pass through relay winding 51. The relay tongue 106 is controlled so as normally to stand between the two contacts 107 and 108. A dot or a block repiesenting a series of dots causes contact at 107 and a dash or a series of dashes cause contact at 108. Contact at 107 causes current from the battery 109 to flow through leads 112 and 113, through magnet 114, and this draws down armature 116. A cam 130 is driven by shaft 64 and bearing against it is a cam follower 118. A. movable selector piece 117 is held against the cam follower .118 in such a manner that the movement of the armature 116 under the action of the magnet 114 causes it to engage with a key 122 carrying contacts 123. The motion of the follower 118 derived from the cam configuration is thus transmitted through the selector piece 117 to the key 122 and this latter carrying contacts 123 causes contact to be made first at 124 and then at 125 depending upon the position of the cam 130.

.Contact is; thus made alternately, at 124 and 125 as long as current in magnet 114 holds down the armature.116. The key 122 in ieality constitutes one lever of an ordinary cable code transmitting key, the other lever of which is key 126..- Therefore, when contacts 127 of key 126 are closed against contact 129 the continued operation of key 122 as described results in the production of a continuous series ofdots or positivecurrent/s impressed by battery 132 through leads 134 and 133 toa cable or line 136 and earth 135. This series of dots lasts as long as the current continues in magnet 114, and,therefore a series of dots received by receiving relay .42 and 43 as a block signal is retransmitted by the devices de-scribed as a perfect series of individual dots. In a similar fashion, the reception of a dash or series of dashes represented by a negative current causes relay tongue 106 to make contact at 108, and thus to energize magnet 115 through leads 110 and 111 by battery 109. Armature 119 and selector piece 120 are thus drawn down into position to cause the motion of the cam 131 to be transmitted through follower 121 and selector piece 120 to key 126. Successive contacts at 128 and 129 are, therefore, made by contact 127 on key 126, resulting in a series of dashes or negative currents being delivered to the cable 136 and earth 135. The function of the apparatus shown in Figure 7 is now completed; perfect mechanically formed signals are transmitted to the new cable 136 consequent upon slightly imperfect received signals from cable 37 and the attainment of this is rendered possible by the synchronous motion of the shaft 64, maintained as described.

It is obvious that the method described above in connection with Figure 7 for the retransmission of cable code signals is equally adapted to the re-transmission of Morse code signals or Baudot signals, or the signals representing any other telegraph code, provided that they possess the necessary qualification of beginning or ending at definite times separated by an integral multiple of a fundamental time period. Certain modifications well known in the art will, of course, be required in the relays leading up to and in the mechanisms of the device eii ecting the re-transmission of the signals, but the actual arrangement of this device does not constitute a part of the present invention.

A great variety of mechanism may be employed for effecting the motion of the phase correcting device, for example a reversing clutch controlling the motion delivered by a continuously rotating shaft, or the differential gearing as shown may be omitted and the phase of the motor driving the controlled shaft be controlled by a control exercised upon the phase of the impulses driving it. In such a case as this latter, the impulses would be obtained fromadjustable cam-operated contacts driven by an auxiliary motor driven from the vibrating reed. Alternatively, invthose cases where great refinement in phase control is notwrequired thephase adjustment may be dispensed with and the speed control exerted directly upon thevibrating reed or whatever controls the speed of the prime mover, asillustrated in connect1on wlth Figure 1 fora shunt motor.

In place of the slip ring shown in Figure.

7, cam or otherwise operated contacts can be used to produce the same result, and this result can be either in the natureofa current reversal as described, or it can be a commutation of current to two apparatus, each operating to eflect correction in one direction.

The speed and phase-controlled shaft (as at 64 in Figure 7) need not be used directly to operate further mechanisms. It may drive cam operated contacts from which any number of impulse motors (phonic wheels) may be driven, in which event all of the ino tors so driven will be maintained in phase and synchronism with the arriving signals, and such motors may then be used in the further handling or retransmission of the received signals, or for any purpose desired.

It is obvious, from the nature of the sys tems described, that signals of some sort are required to maintain synchronism at the two ends of the cable or line, and for this reason it is proposed to equip the transmitter with an attachment providing for the transmission of continuously repeated valve to suppress said current impulses moving in one direction, and means to employ the current impulses moving in the other direction to effect exact synchronism of said distributor with said signal impulses.

8. A system of the class described comprising means to produce signal impulses at intervals, and of duration, which are integral multiples of an elemental period, means to produce through said signal impulses synchronizing impulses at intervals, said synchronizing impulses being also integral multiples of the same elemental period, a distributer kept in synchronism through the action of the signal impulses and the synchronizing impulses to distribute the signal impulses among a plurality of circuits, means responsive to the varying phase relation of the signal impulses and the synchronizing impulses to bring to and maintain at synchronism the movement of the distributor.

9. In a system of the type described, means to emit signal impulses at intervals which are integral multiples of an elemental period, a distributer substantially synchronized with said signal impulses and adapted to apportion the same among a plurality of circuits, means to produce current impulses corre sponding to both ends of each signal, means to suppress such current impulses in one direction, a switch, control circuits, and means including said switch to distribute the remaining impulses to said control circuits, and means actuated through said control circuits to establish the direction of the corrective synchronizing effort of said remaining impulses upon said distributer.

10. In a system according to claim 9, means todrive said switch from the distributer actuating device.

11 In a system accordin to claim 9, means controlled by said switch to govern the phase relation of the distributer to said signal impulses.

12. In a system accordin to claim 9, means controlled by said switch to control the speed of the distributer.

13. In a system according to claim 9, means responsive to the summation of all phase corrections to control the speed of the distributer.

14. In apparatus for transmitting electrical signals which are produced at intervals, and of duration, that are integral multiples of an elemental period, a sending apparatus for the signals at one station, a receivmg apparatus for the signals at another station, a distributing device for the signals at the receiving station, means for actuating the receiving device, means responsive to the incoming signals for producing electrical impulses, means for causing the impulses so produced to be delivered as uni-directional impulses and means for utilizing such unidirectional impulses to synchronize the movements of the actuating means for the distributing device with the incoming signals.

FREDERICK EUGENE PERNOT. 

